The present invention concerns fuel injectors.
German Published Patent Application No. 40 05 455 concerns fuel injectors purporting to have an actuator arranged in an actuator space, and a valve closure member, which can be actuated by the actuator, via a valve needle, and which interacts with a valve seat to form a sealed seat. Apparently, the actuator space is sealed from a combustion chamber by a spring diaphragm fastened to the valve needle. The spring diaphragm is fixed in the valve housing in a circular recess between two housing halves (sections), which are joined to each other by a welded seam.
It is believed that a disadvantage of the foregoing fuel injector of German Published Patent Application No. 40 05 455 is that the elastic spring diaphragm may be deformed by the fuel pressure in the combustion chamber, which is high in comparison with the pressure in the actuator space. In particular, relatively large sheer forces may be applied to the area where the spring diaphragm is fastened to the valve needle, and to the area where the spring diaphragm is fastened to the valve housing. The spring diaphragm is also bent about a small bending radius at an edge of the valve housing, at which the spring diaphragm is fixed, thereby subjecting the spring diaphragm to a point loading. It is believed that the high loading (stress) may sheer off the spring diaphragm at the edge of the recess.
German Published Patent Application No. 195 19 762 purportedly concerns a fuel injector, in which an actuator space is sealed from a combustion chamber by a ring-shaped elastomer seal that is placed between a valve housing and a valve needle. It is believed that a disadvantage of such a fuel injector is that the elastomer seal is not joined to the valve needle or the valve housing. It is also believed that this can result in the elastomer seal being moved or twisted, which may cause the fuel injector to malfunction.
It is also believed that a disadvantage of elastomer seals, and especially of ring-shaped elastomer seals, is that they cannot completely seal the actuator space from the combustion chamber, particularly at high fuel pressures, because of material permeation or propagation. This may lead to a portion of the fuel penetrating into the actuator space. In addition, the materials of elastomer seals may harden at low temperatures.
It is believed that the fuel injector according to an exemplary embodiment of the present invention should provide a resistant, hermetic sealing of the actuator. This should protect the actuator from both the pressure of the fuel and the chemical action of the fuel.
It is also believed to be advantageous that the sealing element is bent over at a bending segment to give the sealing element a U-shaped profile. In this manner, it is believed that the fuel-pressure loading of the sealing element is uniformly distributed, which should have a favorable effect on the service life of the fuel injector.
It is also believed to be advantageous that the valve housing and/or the sealing plate has an uncoiling surface, on which a part of the bending segment of the sealing element is uncoiled in response to the fuel injector being actuated. This even allows large valve-needle lifts to be realized.
The sealing member may be advantageously designed as an actuator top (or head), which at least partially encloses the actuator. The actuator acts, via the actuator head, on a valve needle joined to the valve closure member. This provides a compact design to the fuel injector.
In addition, the sealing member may be advantageously joined to a valve needle. This allows the actuating device to transmit a force, via the sealing member, to the valve needle to both open and close the valve.
Another advantage is believed to be provided by making or manufacturing the sealing element from a metallic material. This provides a seal that is resistant to aging, and whose operability is better ensured over a large temperature range.
Furthermore, it is also believed to be advantageous that the sealing element is made or manufactured by xe2x80x9cdeep-drawingxe2x80x9d. This should enable the fuel injector to be manufactured cost-effectively.